1. Field of the Invention
The present invention relates to a pressure sensor used in such fields as automotives, home appliances, instrumentation and measuring devices, and medical equipment, and relates particularly to a semiconductor pressure sensor in which the peripheral circuitry integrated with the pressure sensor are manufactured as an integrated module.
2. Description of the Prior Art
Hybrid pressure sensor modules are one type of pressure sensor commonly used today in such fields as automotives, home appliances, instrumentation and measuring devices, and medical equipment. An overview of such a conventional pressure sensor is shown in FIG. 18.
The semiconductor pressure sensor 100 shown in FIG. 18 comprises a pressure opening 102 to a molded resin casing 101 having an airtight hollow core. A pressure sensor chip (not shown in the figures) is fastened on a pedestal by an adhesive and is electrically connected using gold wire or other conductor to the lead frame 103 inside the molded resin casing 101, thus forming the pressure sensor module 104. The thick-film circuit board 105 of the semiconductor pressure sensor 100 comprises a thick-film resistor and a printed multiple layer wiring pattern. The clip leads 106 disposed to the thick-film circuit board 105 are used to mount the semiconductor pressure sensor 100 on a printed circuit board.
The pressure sensor chip mentioned above comprises a pressure sensor element and a conversion circuit for converting the pressure detected by the pressure sensor element to an electrical signal. The pressure sensor module 104 is also mounted on the thick-film circuit board 105, and capacitors, resistors, and other chip components 107 that cannot be formed on the pressure sensor chip are surface mounted on the thick-film circuit board 105 and pressure sensor module 104.
The lead frame 103 is electrically connected to the wiring pattern of the thick-film circuit board 105, and the pressure sensor chip is electrically connected to the wiring pattern of the thick-film circuit board 105 by means of the lead frame 103 that is connected by gold wire or other conductor to the wiring pattern of the thick-film circuit board 105. The various terminals of the chip components 107 are electrically connected to the wiring pattern of the thick-film circuit board 105, and the clip leads 106 are also electrically connected to the wiring pattern of the thick-film circuit board 105.
The pressure opening 102 of this configuration is used to conduct a pressure-conveying medium to the pressure sensor element. The pressure-conveying medium applied from the pressure opening 102 enables the pressure sensor element of the pressure sensor module 104 to detect the applied pressure, and the detected pressure is then converted to an electrical signal by the conversion circuit. This semiconductor pressure sensor 100 and the signal processing circuit for accomplishing a particular process based on the electrical signal obtained from the conversion circuit are mounted on a printed circuit board and electrically connected to each other by the wiring pattern of that printed circuit board.
With rising demand for smaller, multiple function semiconductor pressure sensors in various fields, it has become necessary to develop integrated circuits combining the conversion circuit, thick-film circuit board 105, and a multifunction-capable signal processing circuit in what is essentially an IC package configuration. The semiconductor pressure sensor, however, is an element subject to mechanical displacements, and the area surrounding the pressure sensor element must be a hollow or airtight hollow. This has made it necessary to use a premolded hollow package to manufacture integrated pressure sensor modules containing a pressure sensor element and peripheral circuitry IC containing the conversion circuit, thick-film circuit board 105, and signal processing circuit. Furthermore, when the overall package is hollow, the peripheral circuitry IC must be protected because outside air and various pressure-conveying media may enter the airtight hollow chamber depending upon the pressure detection method used.